st: Dot charts: Only 0 possible as lower end of scale?

-graph dot- accepts the yscale(range()) option but it is not possible
to set the lower end of the scale to a number above 0 because values
greater than 0 are ignored. How can I modify both ends of the scale? I
looked at -onewayplot- and -stripplot- from SSC but they only accept
one variable with the by() option. I have to plot data from three
variables.
. sysuse auto
. graph dot mpg trunk, over(foreign)
. graph dot mpg trunk, over(foreign) yscale(r(10 30))
Thanks,
Friedrich
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